An Organic Light Emitting Diode (OLED) and a Polymer Light-emitting Diode (PLED) have particular features such as self-illumination, fast response, wide viewing angle, and being able to be manufactured on a flexible substrate. Thus, a display device based on OLED or PLED is expected to be popular in the field of display in the next few years.
An OLED (or PLED) display backplane includes a substrate, an ITO (Indium Tin Oxide) anode, a light-emitting layer, and a cathode, and its principle of emitting light is: when a voltage is applied, holes and electrons are recombined at the light-emitting layer so as to fall to a lower energy band and release photons whose energy is equal to the energy gap and whose wavelength (color of emitted light) depends on the magnitude of the energy gap of the light-emitting layer.
The light-emitting layer is usually manufactured by printing technique to spread a liquid luminescent material on a specific pixel region. However, size of pixel in existing high resolution products is usually 30 μm×180 μm, while a liquid drop formed by printing has a diameter bigger than 30 μm, which is in a same order of magnitude as the size of the pixel. Therefore, in order to ensure that the printed liquid drops can be successfully and smoothly spread within the pixel region, and meanwhile to avoid a situation that the liquid drops may flow to an adjacent pixel, a pixel define layer (PDL) formed by a double-film structure tends to be applied currently, wherein wider openings are formed in pixel regions in an lower-layer film by means of patterning process, and narrower openings are formed in pixel regions in an upper-layer film by means of patterning process. However, in existing double-layer PDL techniques, two layers of materials are formed separately, and therefore two patterning process are required. As such, the number of masks used is inevitably increased and exposure process is also increased, resulting in enhanced manufacturing oasis, which is unfavorable for mass production.